The Division of Adolescent Medicine, Childrens Hospital Los Angeles is applying for five year funding from the National Institutes of Child Health and Disability (NICHD) and Allergy and Infectious Disease (NIAID) to participate in the Adolescent medicine HIV/AIDS Research Network. The long-term objective of this effort is to achieve a better understanding of HIV disease progression and co-morbidity in adolescents and thus improve health care management for this population. The specific aims are: 1) To describe the natural history of HIV infection in youth 15-19 years of age who have been infected through sexual or injecting drug using practices; 2) To address unresolved questions including, but not limited to, the susceptibility, infectivity and transmissibility of HIV in adolescents, the identification of adolescent-specific clinical markers of HIV disease progression, the effect of HIV on adolescent neuropsychologic function and development, and tahe influence of HIV on adolescent behavioral patterns and risk-taking and health seeking activities; 3) to develop clinical management guidelines for adolescent HIV infection which recognize the unique biological and behavioral features of this group; and 4) to increase adolescent access to appropriate clinical drug and vaccine trials. In order to guarantee the recruitment of a minimum of 20 HIV infected youth that reflect the diversity of Los Angeles County, this consortium proposal involves three other institutions: the University of Southern California medical Center (LAC+USC), and Memorial Miller Childrens Hospital (MMC). Each of these institutions has considerable experience with adolescents and HIV and is dedicated to improving the quality of care for adolescents with HIV infection. The specific research agenda for this cooperative agreement will be developed through the combined efforts of the Adolescent Medicine HIV/AIDS Research Network which will be composed of the Basic Science Group, the Clinical Science Group, the Data/Operations Center and staff from NICHD, NIAID, and HRSA.